Applied Kinesiology - Tennis Serve

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Transcript of Applied Kinesiology - Tennis Serve

By Cassandra Chau and Donna Lu = What does a tennis serve look like? WHAT IS THE PRIMARY PRINCIPLE AND OBJECTIVE? The tennis serve is the most important stroke of the game as it starts off every point! It is completely dependent on the server PLAYER A- 6-4-5PLAYER B- 4-6-3 MECHANICAL OBJECTIVES Balance - The tennis server's balance may influence the serve to be good or bad (Durovic, Lozovina and Mrduljas 2008). locomotion-Navarro and de Subijana (2009) reported that a coordinated locomotion of the lower limb can be fundamental to performing the best serve possible. Projection! Speed + accuracy + range =appropriate trajectory and optimal speed Maximal efforts- Navarro and de Subijana (2009) concluded that high velocities in tennis serves guarantees more winning points, thus increasing the probability of winning a match. Nature of Motions Linear, angular and Curvilinear The tennis serve is a transfer of linear to angular movement.The motion starts from an angular motions as the server twists the trunk enabling the potential energy to be released in the dominant arm which becomes linear motion as it follows through in the same direction of the ball trajectory. Simultaneous movement A tennis serve needs to involve synchronized movements to achieve a biomechanically correct serve. For example, as the non-dominant arm rises to toss the ball the dominant arm swings up in line with the shoulder and forward to make contact with the ball. Sequential Movement Movements that occur within the four phases of tennis serve a conjoined by the kinetic link principle. ...but what is the kinetic link principle? Kinetic Link Principle The Kinetic link principle is the deceleration of one segment to influences the acceleration of an adjoining segment in the kinetic chain. (de Subijana and Navarro 2009). This principle follows the ideology of the Conservation of energy in that energy is created by the ground reaction force opposing gravity and transmitted through the body and into the racket. Manipulation - does the weight of the racket change anything? Nature of Forces Weight- Gravity can influence the player positively or negatively in the way their weight influences their efficiency to move (Durovic, Lozovina and Mrduljas 2008). Propulsive force- It is stressed that the performance must embrace all segments that play a role in the kinetic chain (Elliott, Fleisig, Nicholis and Escamilia 2003). This will ensure for optimal serves and limiting the risk from injury. Normal reaction- the amount of energy produced through the combination of both strength of the player and the execution of the kinetic chain, ultimately influences an equal amount of energy produced into the ball when impacted. As the ball is impacted the force channels the ball to reacted parallel to which it was impacted. Friction- Contact between the tennis ball and the surface of the racket should be limited enough to play little effect in decelerating the ball impulse yet be enough to still hold control. Lift-The lift force is due to the pressure difference between the top and bottom side of a rotating tennis ball (Alam et al. 2007). There are two types of pressure differences – Topspin and Backspin Mechanical Factors Force Inertia Impulse Torque Work Kinetic Energy According to Mitchell, Jones and King (2000), tennis rackets only play a minimal advantage to the speed of the serve. However, more often player achieved higher head speeds with lighter rackets rather than the player’s own racket that they train with. Torque is the tendency of a force to rotate an object. This is evident with in the trunk rotation and pronation of the wrist after contact with the ball. When looking at a tennis serve it is more ideal to produce more power over the same sequential movements. This does not mean the player is to be physically stronger, however they need to generate more kinetic energy by bending the knees deeper. TENNIS SERVE! Injury Implications - overhead motion & repetitive action --> musculoskeletal injury- shoulder and medial elbow-abduction & external rotation --> rotator cuff- anterior shoulder capsule --> secondary impingement, internal impingement, superior labrum anterior posterior (SLAP) lesions, anterior labral injuries, musculotendinosus injuries (Andrew, Bradley & Tibone cited in Abrams et al. 2011) 1. Preparation 2. Wind-Up 3. Point of Contact 4. Recovery 4 Phases Preparation phase: feet approximately shoulder width apartfront foot 45 degrees to baseline, back foot parallel to baselineball & racket placed out in front of body Wind-up phase: Drag-When a ball is reused, it changes the aerodynamics of the ball (Goodwill, Chin and Haake 2004). The worn out ball becomes harder to control as drag is reduced. There are various forces that influence the tennis serve. These include gravity, friction, muscle contraction, weight and ground reaction force. Impulse is equal to the change in momentum thus an increase in force will result in an increase in impulse. The tennis ball will develop an angular momentum if the ball is hit with an off-center impulse (Martin et al. 2012). Work is the force generated to project the ball over the court accurately in the direction of the force applied. - lean on back foot, toss ball keeping arm straight as possible- backswing of racket arm forming L shape with racquet, while bending knees- bring the back foot together with front foot - drop racket behind back until racket head points towards groundelbow goes up, tossing arm comes down- straighten racket arm Point of contact phase: - bent knees straighten and push off ground- racket arm comes up and straightens to hit ball Recovery phase: - racket arm comes down across body to opposite leg- back foot should kick up, then come forward Correct technique Types of serves Flat serve Slice Serve Kick Serve ￼ The aim is to serve it into the opponents service box. classification The tennis serve is a closed skill as it performed in a controlled environment requiring internally paced movements that follow a set of motions. It is performed individually as a discrete skill with a degree of complexity, acquiring repetition for improvement of accuracy.